1. Field of the Invention
This invention relates to an improvement in a process for indirectly alkylating urea.
2. Description of the Prior Art
In order to appreciate the manner in which the present invention represents a marked improvement over the closest prior art, it warrants considering briefly the usefullness N, N-dimethylurea potentially offers as a chemical intermediate. The indicated utility is that of producing unsymmetrical dimethylhydrazine (UDMH), in turn a versatile intermediate for the preparation of surfactants, insecticides, dyes, monomers, etc.; but the most important current use thereof being in the field of liquid propellants for rockets.
Recently, an alternate method to that of the present commercial practice for producing UDMH involving the hydrogenation of nitrosodimethylamine, has been actively sought. This is so because nitrosodimethylamine has been identified as such a powerful carcinogen that in order to provide absolute protection for plant workers a prohibitively expensive installation would be required. An environmentally acceptable alternate method appearing to have commercial merit resides in the modification of the Scheslakoff process (J. Russ. Phys. Chem. Soc., 37, pgs. 1-7, 1905) wherein N, N-dimethylurea is rearranged in accordance with the Hoffman mechanism. As is characteristic of such type rearrangement reactions, optimum yields of product are substantially less than quantitative.
It has hitherto been proposed to prepare N, N-dimethylurea by reacting dimethylamine sulphate with urea in an aqueous system capable of effecting solubilization of the urea. Besides recovery problems, the method suffers because the optimum yields attainable are reportedly in the order of only about half of theoretical. Notwithstanding that the indicated reactants are readily available and relatively inexpensive, the commercial attractiveness of the modified Scheslakoff process for preparing UDMH depends largely on realizing a highly efficient method for preparing N, N-dimethylurea. Accordingly, the foremost objective of the instant invention is to provide such a method.